Method for making particulate slurries and particulate slurry compositions

ABSTRACT

An aqueous slurry composition for use in industries such as the petroleum and pipeline industries includes a particulate, an aqueous liquid and a chemical compound that renders the particulate surface extremely hydrophobic. The slurry is produced by rendering the surface of the particulate extremely hydrophobic during or before making the slurry.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119(e) of U.S.Provisional Application Ser. No. 60/676,316, filed May 2, 2005, andclaims priority from U.S. Provisional Application No. 60/719,597, filedSep. 23, 2005, the contents of each hereby expressly incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an aqueous slurry composition and to a methodof making such a composition.

2. Brief Description of the Prior Art

Aqueous particulate slurries are commonly used or encountered in manyindustries including the petroleum, pipeline, construction and cleaningindustries. Slurries are mixtures normally consisting of particulatesand an aqueous liquid and play an essential role in many industrialoperations. For example, slurries are used when transportingparticulates above ground, from the surface to a subterranean formationor from a subterranean formation to the surface. The most commonly usedparticulates include sand, ceramic particles, carbonate particles, glassspheres, bauxite (aluminum oxide), resin coated particulates and coalparticulates The particulate sizes normally range from about 10 to about100 US mesh, and the particles have densities significantly higher thanthe density of water. For example, the density of sand is at about 2.6g/cm³ while the density of water is 1 g/cm³. Sand is by far the mostcommonly used particulate.

To make relatively stable slurry, particulates must be suspended in aliquid medium for a lengthy period at static or/and dynamic conditions.Convention wisdom tells us that the viscosity or viscoelasticity of theliquid medium must be sufficiently high to be able to suspendparticulates. The most commonly used method for increasing viscosity orviscoelasticity of a liquid medium is by adding a viscosifier, forexample, a natural or synthetic polymer or a viscoelastic surfactant tothe liquid medium. It is not unusual that a polymer is used with afoaming agent in order to take advantage of both viscoelastic andfoaming properties. However, the use of polymers in slurries increasescost and results in operational difficulties. In particularapplications, for example, hydraulic fracturing of subterraneanformations, the use of polymers in slurry impedes oil and gas productiondue to large amounts of residue left in the formation. As forviscoelastic surfactants, although they have fewer residues compared tonormal polymers, their cost is usually much higher. In many otherapplications such as gravel-pack, well completion and sandtransportation through pipelines, it is highly desirable to make stableparticulate slurry without using a viscosifier.

Hydraulic fracturing operations are used extensively in the petroleumindustry to enhance oil and gas production. In hydraulic fracturing, afracturing fluid is injected through a wellbore into a subterraneanformation at a pressure sufficient to initiate fracturing, whichincreases oil and gas production. Frequently, particulates, calledproppants, are suspended in a fracturing fluid and transported into afracture as slurry. Proppants include sands, ceramic particulates, glassspheres, bauxite particulates, resin coated sands and other particulatesknown in the industry. Among them sand is by far the most commonly usedproppant. Fracturing fluids in common use include water-based as well ashydrocarbon-based fluids. In water-based fracturing fluids, a polymer orviscoelastic surfactant is normally employed to increase theviscoelasticity of the fluid. In most case the viscoelastic property ofthe fluids is essential for transporting proppants deep into aformation. At the last stage of the fracturing treatment, fracturingfluid flows back to the surface and the proppants are left in thefracture forming a proppant pack to prevent the fracture from closingafter pressure is released. A proppant-filled fracture provides a highlyconductive channel that allows oil and/or gas to seep through moreefficiently to the wellbore. The conductivity of the proppant pack playsa dominant role in production enhancement. Polymer residues fromfracturing fluids are known to greatly reduce the conductivity of theproppant pack. Compared to polymeric viscosifiers, viscoelasticsurfactants cause less damage to formations and proppant packs. However,they are much more expensive. Accordingly, a need exists for acomposition for efficiently transporting proppants deep into a formationat low cost while at the same time causing little damage to theformation and proppant pack. Grain size, concentration, and the packingpattern of proppants are also important factors in determining theconductivity. Despite extensive research in recent years, limitedprogress has been achieved to maximize the conductivity of a proppantpack in a fracture. Therefore, a need exists for making a compositionfor use in a proppant pack with improved conductivity.

Proppant flowback after fracturing treatments has long been plaguing thepetroleum industry. Flowback reduces the amount of proppants in theformation leading to a less conductive fracture. As disclosed, forexample in U.S. Pat. No. 6,047,772, various methods have been tried tosolve the flowback problem. In one method, resins are used to coat theproppant and make them very tacky. In doing so, the proppant grains tendto agglomerate reducing flowback. This method is not only expensive, butthe tacky resins introduced in the proppant pack tend to reduce itsconductivity. Therefore, there is a need for a composition and methodfor making slurry, which can form a stable proppant pack, which resistsproppant flowback while at the same time has a high conductivity.

When drilling subterranean formations for oil and gas, aqueous-baseddrilling fluids are normally used. During drilling large amounts ofparticles, called cuttings are generated. Cuttings have different sizesranging from fines to pebbles. The drilling fluid is circulated throughthe wellbore to make slurry with the cuttings in situ and transportsthem out of wellbore. In most cases, polymers as well as clays are addedto the drilling fluids to increase their viscosity/viscoelasticity inorder to transport the cuttings efficiently. However, polymers as wellas clay fines, can easily penetrate pores or thin fractures in aformation and reduce formation permeability significantly, especiallynear a wellbore. Reduced formation permeability impedes oil and/or gasproduction. Therefore it is highly desirable to provide a drilling fluidthat can make stable slurry in situ with the cuttings and transport themout of the wellbore, while causing little formation damage.

The escalating price of oil and its alarming depletion rate have causedpeople to consider using coal as an oil substitute. Several factors haveslowed the substitution of coal for oil. One factor is the difficulty intransporting coal cost-effectively over long distance through pipelines.It is therefore highly desirable to provide a composition for makingcoal slurry which is stable, highly fluid and cost-effective totransport.

In oil sand operation massive amount of sands are left after oil isstripped from the sand surface. Finding a more cost effective way totransport sands efficiently over distance through pipelines has longbeen required in the industry. Thus, a composition and a method formaking stable and highly fluid sand slurries at low cost would be quiteuseful.

The object of the present invention is to meet the above defined needsby providing an aqueous slurry composition, which can be used in astable, highly conductive proppant pack, for efficiently transportingproppants into a subterranean formation, and for use in transportingcuttings, coal and sand.

SUMMARY OF THE INVENTION

Accordingly, the invention relates to an aqueous slurry compositioncomprising particulates, an aqueous liquid and a chemical compound thatrenders the surface of the particulates extremely hydrophobic.

The invention also relates to a method of producing an aqueous slurrycomposition comprising the steps of mixing particulates with an aqueousliquid, and rendering the particulate surface extremely hydrophobicduring or before mixing the particulates with the aqueous liquid.

The present invention is based on the discovery that when the surface ofthe particulates becomes extremely hydrophobic, the slurry has severalnovel properties. For example, particulates tend to move cohesivelyinstead as individual grains; the bulk volume of settled particulatestend to be significantly greater than in a slurry formed by conventionmethods under the same conditions; the particulate pack formed tends tohave high conductivity and be easily dewatered, and the slurry tends tobe fluid and stable without using a viscosifier. The larger bulk volumeof the particulate pack indicates a larger porosity and therefore higherconductivity. This is particularly beneficial for improving fracturingtreatment, since, as mentioned above, the conductivity of the proppantpack is the dominant property affecting fracturing treatment. Theextremely hydrophobic surface of the particulate further reduces thedragging force exerted by the fluid and makes it more difficult forproppants to be carried away by the fluid. This is particularlybeneficial for minimizing proppant flowback after fracturing treatments,leading to increased proppant conductivity. In conventional slurry,viscosity or viscoelasticity of the liquid plays the dominant role whilethe interfacial interactions between the particulate surface and theliquid play negligible role. However it is discovered in the presentinvention that when the surface of the particulate becomes extremelyhydrophobic, the interfacial interactions between the surface and theaqueous liquid become increasingly important, and even can play adominant role.

In general, the interfacial interactions between a solid substrate and aliquid mainly depend on the surface properties and the surface tensionof the liquid. Normally the macroscopic properties of a surface can becharacterized by observing the shape of a liquid droplet on the solidsubstrate, which is the result of free energy of the surface, as well asthe free energy of the liquid. When a liquid does not completely wet asurface, it forms an angle θ, which is known as the contact angle. Thecontact angle is the angle formed between a solid substrate and thetangent line at the point of contact between a liquid droplet and thesolid substrate. Contact angle can be measured directly on macroscopic,smooth, nonporous, planar solid substrates by merely placing a dropletof the liquid or solution on the solid substrate and determining thecontact angle by any of number of techniques. It is known that majorityof natural occurred minerals are water-wet. It is also known thatcertain hydrocarbon compounds, for example, some conventional quaternarysurfactants, amine surfactants and cationic polyacrylamides can be usedto reduce the surface energy of certain particulates and make theparticulate surface more hydrophobic. However, the “hydrophobicity”imparted by such compounds is not high enough to be included in the termof “extremely high” hydrophobicity” as in the case of the presentinvention. In the present invention, by “extremely hydrophobic” it meansthat the contact angle of water on the solid substrate is greater thanabout 90°. The chemical compounds that can render the particulatesurface extremely hydrophobic are referred as “extremely hydrophobicrendering compounds” (EHRC). EHRC normally are those compounds thatcontain organosilane or organosilloxane groups or fluoro-organic groups.Because of such groups, EHRC are able to impart hydrophobicity to solidsurface to a level that conventional hydrocarbon surfactants or polymersare not able to achieve.

The slurry can be made on the ground or in situ in a subterraneanformation. The slurry finds numerous applications in many industries,including:

-   -   (a) transporting particulates over various distances, either on        the surface of the ground, from the surface to a subterranean        formation or from a subterranean formation to the surface, and    -   (b) well service operations including stimulation, drilling,        completion, gravel-pack, controlling sand production and the        like.

DETAILED DESCRIPTION OF THE INVENTION

A gas can be added to the slurry. Suitable gases for use in the slurryinclude air, carbon dioxide, nitrogen, methane and mixtures thereof. Thegas can be introduced into the slurry during preparation thereof. Forexample, when the slurry is pumped through a pipe at a sufficient rate,gas such as air can be introduced into the slurry. In the present case,by “aqueous liquids” is meant water, salt solutions, water containing analcohol or other organic solvents, mixtures of water with carbon dioxideand the like. It will be appreciated that the additives other than waterin the aqueous liquid are used in amounts or in a manner that does notadversely affect the present invention. The aqueous fluid can alsocontain polymers which can be linear or cross-linked. For example, inso-called slick-water fracturing, a small amount of polymer is normallyadded to reduce friction during pumping. The size of particulates in thecomposition is about 10-100 US mesh, which is about 150 to 1400 μm. Itshould be understood that the size distribution of particulates can benarrow or wide. Suitable particulates include sand, ceramic, glassbeads, bauxite, resin coated sand, carbonates and coal particulates.

There are several approaches to make particulate surfaces extremelyhydrophobic. One method is to use certain organosilicon compounds torender the surface of particulates such as sands, ceramic particles,glass spheres and bauxite extremely hydrophobic. The organosiliconcompounds include organosiloxane, organosilane, fluoro-organosiloxaneand fluoro-organosilane compounds. The organosiloxane compounds includequaternary siloxane compounds including quaternary polydimethyl siloxaneor diquaternary polydimethyl siloxane and siloxane amines. Theorganosilane compounds include alkylchlorosilane, for examplemethyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane,octadecyltrichlorosilane, alkyl-alkoxysilane compounds, for examplemethyl-, propyl-, isobutyl- and octyltrialkoxysilanes. Thefluoro-organosilane compounds include2-(n-perfluoro-octyl)-ethyltriethoxysilane, and perfluoro-octyldimethylchlorosilane. Other types of chemical compounds which can be used torender particulate surface extremely hydrophobic are certainfluoro-substituted compounds, for example certain fluoro-organiccompounds. Examples are described in U.S. Pat. Nos. 4,564,456;4,689,085; 5,098,979; 5,209,775; 5,240,760; 5,359,104; 6,132,638 and6,830,811 and Canadian Patent No. 2,213,168. In some cases, when usingthe composition described herein, a catalyst might be preferred to speedup the interaction between an EHRC and the particulate surface. Fordifferent particulates, certain EHRC may be preferred over others.

There are many types of organosilicon compounds which can be used toimpart extreme hydrophobicity to particulate surfaces. One example is anorganosilane which can be represented by the formula:R_(n)SiX_((4-n))  (I)wherein R is an organic radical containing 1-50 carbon atoms, X is ahalogen, alkoxy, acyloxy or amine containing 1-50 carbon atoms and n hasa value of 1-3. Examples of suitable organosilanes include:

-   -   CH₃SiCl₃, CH₃CH₂SiCl₃, (CH₃)₂SiCl₂, (CH₃CH₂)₂SiCl₂,        (C₆H₅)₂SiCl₂, (C₆H₅)SiCl₃, (CH₃)₃SiCl, CH₃HSiCl₂, (CH₃)₂HSiCl,        CH₃SiBr₃, (C₆H₅)SiBr, (CH₃)₂SiBr₂, (CH₃CH₂)₂SiBr₂, (C₆H₅)SiBr₂,        (CH₃)₃SiBr, CH₃HSiBr₂, (CH₃)₂HSiBr, Si(OCH₃)₄, CH₃Si(OCH₃)₃,        CH₃Si(OCH₂CH₃)₃, CH₃Si(OCH₂CH₂CH₃)₃CH₃Si[O(CH₂)₃CH₃]₃,        CH₃CH₂Si(OCH₂CH₃)₃, C₆H₅Si(OCH₃)₃, C₆H₅CH₂Si(OCH₃)₃,        C₆H₅Si(OCH₂CH₃)₃, CH₂═CHCH₂Si(OCH₃)₃, (CH₃)₂Si(OCH₃)₂,        (CH₃)₂Si(OCH₂CH₃)₂, (CH₃)₂Si(OCH₂CH₂CH₃)₂,        (CH₃)₂Si[O(CH₂)₃CH₃]₂, (CH₃CH₂)₂Si(OCH₂CH₃)₂, (C₆H₅)₂Si(OCH₃)₂,        (C₆H₅CH₂)₂Si(OCH₃)₂, (C₆H₅)₂Si(OCH₂CH₃)₂, (CH₂═CH₂)Si(OCH₃)₂,        (CH₂═CHCH₂)₂Si(OCH₃)₂, (CH₃)₃SiOCH₃, CH₃HSi(OCH₃)₂,        (CH₃)₂HSi(OCH₃), CH₃Si(OCH₂CH₂CH₃)₃, CH₂═CHCH₂Si(OCH₂CH₂OCH₃)₂,        (C₆H₅)₂Si(OCH₂CH₂OCH₃)₂, (CH₃)₂Si(OCH₂CH₂OCH₃)₂,        (CH₂═CH₂)₂Si(OCH₂CH₂OCH₃)₂, (CH₂═CHCH₂)₂Si(OCH₂CH₂OCH₃)₂,        (C₆H₅)₂Si(OCH₂CH₂OCH₃)₂, CH₃Si(CH₃COO)₃,        methyldiethylchlorosilane, butyltrichlorosilane        diphenyldichlorosilane, vinyltrichlorosilane,        methyltrimethoxysilane, vinyltriethoxysilane,        vinyltris(methoxyethoxy)silane,        methacryloxypropyltrimethoxysilane,        glycidoxypropyltrimethoxysilane, aminopropyltriethoxysilane,        divinyldi-2-methoxysilane, ethyltributoxysilane,        isobutyltrimethoxysilane, hexyltrimethoxysilane,        n-octyltriethoxysilane, dihexyldimethoxysilane;        trichloro-octadecylsilane and quaternary ammonium silane        including 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium        chloride, 3-(trimethylethoxysilylpropyl)didecylmethyl ammonium        chloride and triethoxysilyl soyapropyl dimonium chloride.

Different polysiloxane compounds can also be useful for the presentinvention. Polysiloxanes modified with organic cationic or amphotericgroups including organic betaine polysiloxanes and organic quaternarypolysiloxanes are examples. One type of betaine polysiloxane orquaternary polysiloxane is represented by the formula:

wherein each of the groups R₁ to R₆, and R₈ to R₁₀ represents an organicradical containing 1-6 carbon atoms, typically a methyl group, R₇represents an organic betaine group for betaine polysiloxane, forexample betaine polysiloxane copolyol, or an organic quaternary groupfor quaternary polysiloxane, and may contain a hydroxyl group or otherfunctional groups containing N, P or S, and have different numbers ofcarbon atoms, and m and n are from 1 to 200. For example when R₇ is anorganic quaternary group it can be represented by the group:

wherein R¹, R², R³ are alkyl groups with 1 to 22 carbon atoms or alkenylgroups with 2 to 22 carbon atoms. R⁴, R⁵, R⁶ are alkyl groups with 1 to22 carbon atoms or alkenyl groups with 2 to 22 carbon atoms; R⁶ is —O—or the NR⁸ group, R⁸ being an alkyl or hydroxyalkyl group with 1 to 4carbon atoms or a hydrogen group; Z is a bivalent hydrocarbon group withat least 4 carbon atoms, which may have a hydroxyl group and may beinterrupted by an oxygen atom, an amino group or an amide group; x is 2to 4; The R¹, R², R³, R⁴, R⁵, R⁶ may be the same or the different, andX⁻ is an inorganic or organic anion. Such compounds are commercialavailable from Degussa Corporation and Dow Corning Corporation.

Other example of organo-modified polysiloxanes include di-betainepolysiloxanes and di-quaternary polysiloxanes, which can be representedby the formula:

wherein the groups R₁₂ to R₁₇ each represents an organic radicalcontaining 1-6 carbon atoms, typically a methyl group, both R₁₁ and R₁₈group represent an organic betaine group for di-betaine polysiloxanes oran organic quaternary group for di-quaternary, for example Quaternium 80(INCl), and may contain a hydroxyl group or other functional groupscontaining N, P or S, and have different numbers of carbon atoms, and mis from 1 to 200. For example when R₁₁ and R₁₈ is an organic quaternarygroup it can be represented by the group:

wherein R¹, R², R³, R⁴, R⁵, R⁶, Z, X and x are defined above. Suchcompounds are commercially available from Degussa Corporation or DowCorning Corporation. It should be apparent to those skilled in the artthat there are different mono- and di-quaternary polysiloxanes, mono-and di-betaine polysiloxanes and other organo-modified polysiloxanecompounds which can be useful in the present invention. These compoundsare widely used in personal care products, for example in U.S. Pat. Nos.4,054,161; 4,891,166; 5,235,082; 5,306,434; 5,474,835; 5,616,758;6,277,361 and 6,482,969.

Another example of organosilicon compounds which can be used in thecomposition of the present invention are fluoro-organosilane orfluoro-organosiloxane compounds in which at least part of the organicradicals in the silane or siloxane compounds are fluorinated. Suitableexamples are fluorinated chlorosilanes or fluorinated alkoxysilanesincluding 2-(n-perfluoro-octyl)ethyltriethoxysilane,perfluoro-octyldimethyl chlorosilane, (CF₃CH₂CH₂)₂Si(OCH₃)₂,CF₃CH₂CH₂Si(OCH₃)₃, (CF₃CH₂CH₂)₂Si(OCH₂CH₂OCH₃)₂ andCF₃CH₂CH₂Si(OCH₂CH₂OCH₃)₃.

Other compounds which can be used are fluoro-substituted compounds, forexample, certain fluoro-organic compounds.

The slurry according to the present invention can be prepared, forexample, by mixing water with the particulates and an EHRC. Normallysufficient shear is needed. Alternatively, the particulates can be firsttreated by contacting a fluid medium containing an EHRC to cause theparticulates to become extremely hydrophobic and then separating theparticulates from the medium. The fluid medium can be a liquid or a gas.The hydrophobic particulates can later be used to make slurry. Water isthe most preferred aqueous liquid for making the slurry. Certain salts,some conventional hydrocarbon surfactants or polymers can be added tothe slurry at concentrations and in a manner which would not adverselyaffect the slurry. For example, when conventional surfactants, polymersor other additives are added to the slurries, one should try to avoidforming insoluble precipitates with the EHRC, or making large changes tothe surface energy of the particulate surface, or greatly reducing thesurface tension of the aqueous liquid. In some cases, a very low surfacetension of the aqueous liquid is not desirable. When the surface tensionof the liquid is too low, more water can be added or some of the aqueousliquid can be replaced with new water.

The slurries can be prepared on surface (above ground) or in asubterranean formation where the particulates, an aqueous fluid, and anEHRC, for example a di-quaternary polysiloxane, are mixed in situ.Examples of situations where in situ mixing is used include drilling andwellbore cleanout operations. Alternatively, the particulates can befirst mixed with a liquid in which an EHRC is dispersed or dissolved andthen the particulates separated from the liquid or dried. The thustreated particulates can subsequently be used to make the slurry.Various proppants including sands, ceramic particulates or resin coatedsands can be treated according to the present invention duringmanufacturing process. The thus prepared hydrophobic particulates can beused as proppants in fracturing operations. Depending on the amount andsize of the particulates in the slurry, a wide range of EHRCconcentration can be used to render the particulate surface extremelyhydrophobic. Usually the amount of EHRC added is very small and has noapparent effect on the viscosity of the liquid to which it is added. Forexample, the concentration of EHRC in the slurry can be as low as a fewppm to hundreds of ppm. In most applications, it is unnecessary to addEHRC in an amount larger than 1 percent of the total liquid.

The following examples serve to illustrate the concepts of the presentinvention:

EXAMPLE 1

50 ml of water and 50 grams of 20/40 mesh fracturing sands were addedinto each of two glass bottles (200 ml). 0.5 ml of Tegopren 6923, adi-quaternary ploysiloxane from Degussa Corp., was added into one of thebottles and the other bottle was used as control. The bottles werevigorously shaken and then let stand to allow sands settle down. Thevolumes of the settled sands in the two bottles were compared. In thebottle containing Tegopren 6923, the volume of the settled sands wasabout 40 percent greater than the one without. When the bottles weretilted, the settled sands in the bottle with straight water fended tomove as individual sand grains, while the settled sands containingTegopren 6923 tended to move as cohesive masses.

EXAMPLE 2

50 ml water, 50 grams of 20/40 mesh fracturing sands, 0.5 ml of Tegopren6923 and 0.1 ml of Aquard 18-50, a hydrocarbon quaternary ammonium saltfrom Akzo Nobel Corp., was mixed into a glass bottle (200 ml). Thebottles were vigorously shaken and then let stand to allow sands settledown. The sand grains immediately following agitation were fullydistributed in water making stable slurry. After one hour, about halfamount of sands settled down to the bottom while the other half wasfloating on the top.

EXAMPLE 3

100 ml of water and 50 grams of 20/40 mesh ceramic proppants were addedinto each of two glass bottles (200 ml). 0.5 ml of TEGO Betaine 810, acapryl/capramidopropyl betaine from Degussa Corp., and 1 ml of asolution containing 20% Tegopren 6924, a di-quaternary ploysiloxane fromDegussa Corp., and 80% of ethylene glycol mono-butyl ether were addedinto one of the bottles, and the other bottle was used as control. Thebottles were vigorously shaken and then let stand to allow proppantssettle down. In the one containing Tegopren 6924 about 25% of proppantswas floating on the top and the remaining 75% settled on the bottom. Thevolume of the 75% settled proppants was still significantly larger thanthe control one. When the bottles were tilted, the settled proppants inthe bottle with straight water tended to move as individual grains,while the settled proppants containing Tegopren 6924 tended to move ascohesive masses.

EXAMPLE 4

100 ml of water and 50 grams of 40/70 mesh fracturing sand were addedinto each of two glass bottles (200 ml). 0.1 ml of Tegopren 6924 and 0.1ml of TEGO Betaine 810, were added and further added 2 wt % KCl. Theother bottle was used as control. The bottles were vigorously shaken andthen let stand to allow sands settle down. The volumes of the settledsands in the two bottles were compared. In the bottle containingTegopren 6924, about 15% of sands was floating on the top and theremaining 85% settled on the bottom. The volume of the 85% settled sandwas still significantly larger than the control one. When the bottleswere tilted, the settled sands in the bottle with straight water tendedto move as individual grains, while the settled sands containingTegopren 6924 tended to move as cohesive masses.

EXAMPLE 5

100 ml of water and 50 grams of 40/70 mesh fracturing sand were addedinto each of two glass bottles (200 ml). 0.5 ml of TEGO Betaine 810 and1 ml of a solution containing 20% Tegopren 6924 and 80% of ethyleneglycol mono-butyl ether were added into one of the bottles. Afterthoroughly mixing the sands were separated from the liquid and dried atroom temperature. The pre-hydrophobonized sands were mixed with 100 mlwater and shaken vigorously. In the bottle containing Tegopren 6924,about 40% of sands was floating on the top and the remaining 60% settledon the bottom. The volume of the 60% settled sand was stillsignificantly larger than the control one. When the bottles were tilted,the settled sands in the bottle with straight water tended to move asindividual grains, while the settled sands containing Tegopren 6924tended to move as cohesive masses.

EXAMPLE 6

100 ml of water and 50 grams of coal particulates were added into eachof two glass bottles (200 ml). 0.5 ml of TEGO Betaine 810 and 1 ml of asolution containing 20% Tegopren 6924 and 80% of ethylene glycolmono-butyl ether were added into one of the bottles. The other bottlewas used as control. In the bottle containing Tegopren 6924, about 45%of coal particulates was floating on the top and the remaining 55%settled on the bottom. The volume of the 55% settled coal particulateswas about 15% smaller than the control one.

EXAMPLE 7

100 ml of water and 50 grams of 40/70 mesh fracturing sand were addedinto each of two glass bottles (200 ml). 0.03 ml of Maquat QSX, aquaternary silane compound characterized as triethoxysilyl soyapropyldimonium chloride in butylene glycol, was added into one of the bottles.The other bottle was used as control. After being thoroughly mixed theliquid above the settled sand was discarded and replaced with sameamount of water. The bottles were vigorously shaken and then let standto allow sands settle down. The volumes of the settled sands in the twobottles were compared. In the bottle containing Maquat QSX, about 5% ofsands was floating on the top and remain 95% settled on the bottom. Thevolume of the 95% settled sand was still significantly larger than thecontrol one. When the bottles were tilted, the settled sands in thebottle with straight water tended to move as individual grains, whilethe settled sands containing Maquat QSX tended to move as cohesivemasses.

EXAMPLE 8

100 ml of water and 50 grams of 20/40 mesh resin coated sands were addedinto each of two glass bottles (200 ml). 0.5 ml of TEGO Betaine 810 and1 ml of a solution containing 20% Tegopren 6924 and 80% of ethyleneglycol mono-butyl ether were added into one of the bottles, and theother bottle was used as control. The bottles were vigorously shaken andthen let stand to allow resin coated sands settle down. The volume ofsettled sands containing Tegopren 6924 is about twice of that in thecontrol one.

As mentioned above, the present invention is particularly useful in manyapplications in the petroleum industry as well as in other industries.Examples include various well service operations including hydraulicfracturing, gravel pack, wellbore cleanout and drilling, particulatetransportation through pipe lines and sand blasting.

When used in a hydraulic fracturing operation, a large amount ofproppants can effectively be transported into subterranean formationwithout using a viscosifier. It is not only cost-effective but alsoeliminates damage to the formation and proppant pack caused by polymerresidues. An EHRC, for example a di-quaternary polysiloxane can be addedto a water-based fracturing fluid containing proppants to make theslurry and then pumped into the formation during the proppant stage.Various aqueous fracturing fluids including water, brine, linear polymerfluid, cross-linked polymer fluid and viscoelastic surfactant fluid canbe used. It is particularly beneficial to use the slurry in so-calledslick-water fracturing treatment. In conventional slick-water fracturingoperations, due to the low viscosity of the fluid, only lowconcentration of proppants can be effectively pumped deep into aformation, and moreover the proppants tend to settle down on the bottomof the fracture, resulting in lower conductivity. With the compositionof the present invention, high concentration of proppants can easily bepumped deep into a formation and the proppants are more evenlydistributed in the fracture, leading to improved conductivity of theproppant pack. During the fracturing operation, the EHRC can be addedon-the-fly. Optionally, one can use proppants already rendered extremelyhydrophobic in the fracturing operation. Another benefit of the slurryof the present invention is that the fluid is readily re-useable afterflow back from a well. This has great significance considering there islimited water supply in a number of places.

The present invention also provides a new method for preventing proppantflowback after a fracturing treatment. In field operations, proppantscan be pumped into a formation using the composition of the presentinvention. Various aqueous fracturing fluid, for example water, brine, alinear polymer fluid, a cross-linked polymer fluid or a viscoelasticsurfactant fluid can be used. Alternatively, a fluid medium containingan EHRC can be pumped into the formation following the proppant stage tomix with particulates already in the formation. The particulates in theslurry tend to move cohesively in contrast to conventional slurriesunder the same conditions. It is worth noting that the cohesivenessamong the proppant grains in the present slurry originates fromhydrophobic interactions, instead of tackiness as described, for examplein U.S. Pat. No. 6,047,772.

The slurry of the present invention is particularly useful ingravel-pack operations where sand slurry is normally pumped into awellbore to prevent excessive amount of sands from flowing into thewellbore from the formation. The present method is cost effective andthe sand pack formed has a high conductivity. Similarly, the slurry canalso be used in so-called formation consolidation operations. In such anoperation, a fluid containing an EHRC is injected into a formation toincrease cohesiveness among sand grains to consolidate the formation andto reduce sand production.

In drilling operations, an EHRC can be added directly to a water-baseddrilling fluid. It is particularly useful when the EHRC is added towater or brine for use as a drilling fluid. During a drilling operation,the fluid forms slurry in situ with cuttings and transports the cuttingsout of the wellbore. A gas such as nitrogen or carbon dioxide can bemixed with the slurry during drilling. Since it is not necessary to usepolymers or clays to viscosify the fluid, there is much less formationdamage. Moreover, the cuttings can be easily removed on the surface andthe fluid becomes readily re-useable. Different formations includingsandstone, carbonate, shale and coal seams can be drilled using theslurry of the present invention.

Similarly in wellbore cleanout operations, water or brine containing anEHRC can circulate in the wellbore and form slurry with debris in situ.The debris is subsequently transported out of the wellbore as slurry.The fluid is readily re-useable after separation from the debris.

For transporting particulates through pipelines slurry can be preparedby mixing the ingredients and then pumping the slurry through thepipeline.

1. An aqueous slurry composition comprising: (a) water; (b)particulates; and (c) a chemical compound for rendering the surface ofthe particulates extremely hydrophobic.
 2. The composition of claim 1,wherein the particulates are selected from the group consisting of sand,resin coated sand, ceramic, carbonate, bauxite, shale and coalparticulates.
 3. The composition of claim 1, wherein the particulatesare subterranean formation particulates.
 4. The composition of claim 1,wherein the chemical compound is selected from the group consisting ofan organosilane, an organosiloxane, a fluoro-organosilane, afluorro-organosiloxane and a fluoro-organic compound.
 5. The compositionof claim 1, wherein the chemical compound is an organosilane having theformulaR_(n)SiX_((4-n)) wherein R is an organic radical having 1-50 carbonatoms, X is a halogen, alkoxy, acyloxy or amine and n has a value of1-3.
 6. The composition of claim 5, wherein the organosilane is selectedfrom the group consisting of: CH₃SiCl₃, CH₃CH₂SiCl₃, (CH₃)₂SiCl₂,(CH₃CH₂)₂SiCl₂, (C₆H₅)₂SiCl₂, (C₆H₅)SiCl₃, (CH₃)₃SiCl, CH₃HSiCl₂,(CH₃)₂HSiCl, CH₃SiBr₃, (C₆H₅)SiBr, (CH₃)₂SiBr₂, (CH₃CH₂)₂SiBr₂,(C₆H₅)SiBr₂, (CH₃)₃SiBr, CH₃HSiBr₂, (CH₃)₂HSiBr, Si(OCH₃)₄,CH₃Si(OCH₃)₃, CH₃Si(OCH₂CH₃)₃, CH₃Si(OCH₂CH₂CH₃)₃)CH₃Si[O(CH₂)₃CH₃]₃,CH₃CH₂Si(OCH₂CH₃)₃, C₆H₅Si(OCH₃)₃, C₆H₅CH₂Si(OCH₃)₃, C₆H₅Si(OCH₂CH₃)₃)₃,CH₂═CHCH₂Si(OCH₃)₃, (CH₃)₂Si(OCH₃)₂, (CH₃)₂Si(OCH₂CH₃)₂,(CH₃)₂Si(OCH₂CH₂CH₃)₂, (CH₃)₂Si[O(CH₂)₃CH₃]₂, (CH₃CH₂)₂Si(OCH₂CH₃)₂,(C₆H₅)₂Si(OCH₃)₂, (C₆H₅CH₂)₂Si(OCH₃)₂, (C₆H₅)₂Si(OCH₂CH₃)₂,(CH₂═CH₂)Si(OCH₃)₂, (CH₂═CHCH₂)₂Si(OCH₃)₂, (CH₃)₃SiOCH₃, CH₃HSi(OCH₃)₂,(CH₃)₂, HSi(OCH₃), CH₃Si(OCH₂CH₂CH₃)₃, CH₂═CHCH₂Si(OCH₂CH₂OCH₃)₂,(C₆H₅)₂Si(OCH₂CH₂OCH₃)₂, (C H₃)₂Si(OCH₂C H₂OCH₃)₂, (CH₂═CH₂)₂Si(OC H₂CH₂OCH₃)₂, (CH₂═CHCH₂)₂Si(OCH₂CH₂OCH₃)₂, (C₆H₅)₂Si(OCH₂CH₂OCH₃)₂,CH₃Si(CH₃COO)₃, methyldiethylchlorosilane, butyltrichlorosilanediphenyldichlorosilane, vinyltrichlorosilane, methyltrimethoxysilane,vinyltriethoxysilane, vinyltris(methoxyethoxy)silane,methacryloxypropyltrimethoxysilane, glycidoxypropyltrimethoxysilane,aminopropyltriethoxysilane, divinyldi-2-methoxysilane,ethyltributoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane,n-octyltriethoxysilane, dihexyldimethoxysilane;trichloro-octadecylsilane, 3-(trimethoxysilyl)propyldimethyloctadecylammonium chloride, 3-(trimethylethoxysilylpropyl)didecylmethyl ammoniumchloride and triethoxysilyl soyapropyl dimonium chloride.
 7. Thecomposition of claim 1, wherein the chemical compound is anorgano-siloxane having the formula:

wherein each of R₁ to R₆ and R₈ to R₁₀, represents an organic radicalcontaining 1-6 carbon atoms, typically a methyl group, R₇ represents anorganic betaine group for an organic betaine polysiloxane or an organicquaternary group for an organic quaternary polysiloxane, and m and n arefrom 1 to
 200. 8. The composition of claim 7, wherein the chemicalcompound is an organic betaine polysiloxane.
 9. The composition of claim8, wherein the chemical compound is an organic betaine polysiloxane, andthe values of m and n are from 1 to
 100. 10. The composition of claim 9,wherein the chemical compound is an organic betaine polysiloxane,wherein each of R₁ to R₆ and R₈ to R₁₀ is a methyl group and the valuesof m and n are from 1 to
 100. 11. The composition of claim 7, whereinthe chemical compound is an organic quaternary polysiloxane.
 12. Thecomposition of claim 11, wherein the chemical compound is an organicquaternary polysiloxane, and the values of m and n are from 1 to 100.13. The composition of claim 12, wherein the chemical compound is anorganic quaternary polysiloxane, and each of R₁ to R₆ and R₈ to R₁₀ is amethyl group and the values of m and n are from 1 to
 100. 14. Thecomposition of claim 1, wherein the chemical compound is anorgano-siloxane having the formula:

where R₁₂ to R₁₇ each represents an organic radical containing 1-6carbon atoms, typically a methyl group, R₁₁ and R₁₈ each represents anorganic betaine group for a di-betaine polysiloxane or an organicquaternary group for a di-quaternary polysiloxane, and m is 1 to 200.15. The composition of claim 14, wherein the chemical compound is adi-betaine polysiloxane.
 16. The composition of claim 15, wherein thechemical compound is a di-betaine polysiloxane and the values of m arefrom 1 to
 100. 17. The composition of claim 16, wherein each of R₁₂ toR₁₇ represents a methyl group and the m is from 1 to
 100. 18. Thecomposition of claim 14, wherein the chemical compound is adi-quaternary polysiloxane.
 19. The composition of claim 18, wherein thechemical compound is a di-quaternary polysiloxane, and the values of mare from 1 to
 100. 20. The composition of claim 19, wherein each of R₁₂to K₁₇ represents a methyl group and the m is from 10 to
 100. 21. Thecomposition of claim 1 includes a gas.
 22. The composition of claim 21,wherein the gas is selected from the group consisting of air, nitrogen,carbon dioxide, methane and mixtures thereof.
 23. A method of producingan aqueous slurry composition comprising the step of mixing water,particulates and a chemical compound for rendering the surface of theparticulates extremely hydrophobic.
 24. The method of claim 23, whereinthe particulates are selected from the group consisting of sand, resincoated sand, ceramic, carbonate, bauxite, shale and coal particulates.25. The method of claim 23, wherein the chemical compound is selectedfrom the group consisting of an organosilane, an organosiloxane, afluoro-organosilane, a fluoro-organosiloxane and a fluoro-organiccompound.
 26. The composition of claim 25, wherein the chemical compoundis an organosilane having the formula:R_(n)SiX_((4-n)) wherein R is an organic radical having 1-50 carbonatoms, X is a halogen, alkoxy, acyloxy or amine and n has a value of1-3.
 27. The composition of claim 25, wherein the chemical compound isan organo-polysiloxane having the formula:

wherein each of R₁ to R₆ and R₈ to R₁₀, represents an organic radicalcontaining 1-6 carbon atoms, typically a methyl group, R₇ represents anorganic betaine group for an organic betaine polysiloxane or an organicquaternary group for an organic quaternary polysiloxane, and m and n arefrom 1 to
 200. 28. The composition of claim 27, wherein the particulatesare sands.
 29. The composition of claim 25, wherein the chemicalcompound is an organo-siloxane having the formula:

where R₁₂ to R₁₇ each represents an organic radical containing 1-6carbon atoms, typically a methyl group, R₁₁ and R₁₈ each represents anorganic betaine group for a di-betaine polysiloxane or an organicquaternary group for a di-quaternary polysiloxane, and m is 1 to 200.30. The composition of claim 29, wherein the particulates are sands. 31.The method of claim 23, including the step of subjecting the slurrycomposition to shear in the presence of a gas.
 32. The method of claim31, wherein the gas is selected from the group consisting of air,nitrogen, carbon dioxide, methane and mixtures thereof.
 33. The methodof claim 23, including the steps of contacting the particulate with amedium containing the chemical compound to render the particulatehydrophobic, separating the particulate from the medium; and blendingthe hydrophobic particulate with water.
 34. The method of claim 33,including the step of subjecting the slurry composition to shear in thepresence of a gas.
 35. The method of claim 33, wherein the gas isselected from the group consisting of air, nitrogen, carbon dioxide,methane and mixtures thereof.
 36. The composition of claim 33, whereinthe chemical compound is an organo-polysiloxane having the formula:

wherein each of R₁ to R₆ and R₈ to R₁₀, represents an organic radicalcontaining 1-6 carbon atoms, typically a methyl group, R₇ represents anorganic betaine group for an organic betaine polysiloxane or an organicquaternary group for an organic quaternary polysiloxane, and m and n arefrom 1 to
 200. 37. The composition of claim 36, wherein the particulatesare sands.
 38. The composition of claim 33, wherein the chemicalcompound is an organo-siloxane having the formula:

where R₁₂ to R₁₇ each represents an organic radical containing 1-6carbon atoms, typically a methyl group, R₁₁ and R₁₈ each represents anorganic betaine group for a di-betaine polysiloxane or an organicquaternary group for a di-quaternary polysiloxane, and m is 1 to 200.39. The composition of claim 38, wherein the particulates are sands. 40.A method of producing an aqueous slurry composition for a well serviceoperation in various formations, comprising the step of mixing water,particulates and a chemical compound for rendering the surface of theparticulates extremely hydrophobic.
 41. The well service operation inclaim 40 is selected from the group consisting of hydraulic fracturing,drilling, completion and sand pack operation.
 42. The method of claim40, including the step of subjecting the slurry composition to shear inthe presence of a gas.
 43. The fluid in claim 40 can be re-used afterseparated from the particulates.
 44. The composition of claim 40,wherein the chemical compound is an organo-polysiloxane having theformula:

wherein each of R₁ to R₆ and R₈ to R₁₀, represents an organic radicalcontaining 1-6 carbon atoms, typically a methyl group, R₇ represents anorganic betaine group for an organic betaine polysiloxane or an organicquaternary group for an organic quaternary polysiloxane, and m and n arefrom 1 to
 200. 45. The composition of claim 40, wherein the chemicalcompound is an organo-siloxane having the formula:

where R₁₂ to R₁₇ each represents an organic radical containing 1-6carbon atoms, typically a methyl group, R₁, and R₁₈ each represents anorganic betaine group for a di-betaine polysiloxane or an organicquaternary group for a di-quaternary polysiloxane, and m is 1 to 200.46. A method of producing an aqueous slurry composition for transportingparticulates through a pipeline, comprising the step of mixing water,particulates and a chemical compound for rendering the surface of theparticulates extremely hydrophobic, and pumping the slurry through thepipeline.
 47. The composition of claim 46, wherein the particulates aresands.
 48. The composition of claim 46, wherein the particulates arecoal particulates.